I believe Vince made the deal with his dad to buy it in 1982, but I don't think he owned it "free and clear" until 1983 as that's when he started making all the big moves. He didn't pay for it all at once; payments were made out over time and the agreement was if he defaulted, ownership would revert back to his dad and his partners.

Jim Crockett had a similar deal with Bill Watts when he bought the UWF from him in 1987. But Crockett was in so much trouble that he only paid Watts something like a third of what they agreed upon. I believe when Turner took over from Crockett, they assumed the debts as well and ended up paying Watts the rest of what he was owed.